Conventionally, with reference to FIG. 1, a turbine engine 1, as disclosed in patent application FR 2902142 by SNECMA, extends axially along an axis X-X and comprises an inner casing 11, an inter-duct casing 12 and an outer casing 13 so as to delimit a primary duct V1 between the inter-duct casing 12 and the inner casing 11 and a secondary duct V2 between the inter-duct casing 12 and the outer casing 13. In other words, the secondary duct V2 and the primary duct V1 are annular and are separated by the inter-duct casing 12.
The turbine engine 1 comprises a rotary shaft, which upstream comprises a movable fan 2 for compressing an incident air flow F, the movable fan 2 comprising radial vanes 20, the free end of which is facing the outer casing 13 of the turbine engine 1 so as to compress an air flow at least in the secondary duct V2 and, preferably, also in the primary duct V1. Conventionally, the turbine engine 1 is called ducted-fan turbine engine.
The air flow circulating in the primary duct V1 is conventionally compressed by compressor stages of the turbine engine 1 before entering the combustion chamber. The combustion energy is recovered by turbine stages, which help to drive the compressor stages and the upstream movable fan 2. The air flow circulating in the secondary duct V2 for its part contributes to the thrust of the turbine engine 1.
Conventionally, the secondary duct V2 comprises, downstream of the movable fan 2, fixed radial vanes or stator vanes 3, which are known to a person skilled in the art as “Outlet Guide Vanes (OGV)”, to straighten the air flow F0 deflected by the movable fan 2 as it rotates. Similarly, downstream of the movable fan 2, the primary duct V1 comprises fixed radial vanes or stator vanes 4, which are known to a person skilled in the art as “Inlet Guide Vanes (IGV)”. A “fixed vane” or “stator vane” is understood to be a vane that is not set into rotation about the axis X-X of the turbine engine 1, i.e. contrary to a movable vane or rotor of a rotor stage of the turbine engine 1.
To improve the performance of this turbine engine, it has been proposed for a plurality of variable-pitch radial stator vanes to be mounted upstream of the movable fan, the variable-pitch radial vanes being configured to deflect axial incident air and the movable fan being configured to axially straighten this deflected air in the secondary duct.
Introducing variable-pitch radial stator vanes particularly allows the performance of the turbine engine to be improved for a set of flight conditions and for its acoustic impact to be reduced. However, the devices for adjusting the variable-pitch of vanes that are already commonly present in turbine engines only allow a uniform variation of the pitch of the vanes. Indeed, each vane is connected to a control ring by a lever or connecting rod. The control ring exerts the same displacement on the end of each lever. Since they are of equal length, all the levers therefore pivot by the same angular amplitude. An example of a variable-pitch stator vane of this type is disclosed in document FR 2688827 by the applicant. However, they do not allow the pitch of the vanes to be dynamically adjusted by azimuth to any lack of homogeneity in the incoming flow.
Therefore, a requirement exists for individually adjusting the pitch of the fixed radial vanes in order to take into account any distortions in the air flow entering the turbine engine, for example due to boundary layer ingestion or due to the presence of side wind. The fact that the pitch of the vanes can be modified individually as a function of their azimuthal position in the turbine engine thus allows the flow entering the fan to be adapted both to the flight conditions (take-off, cruising, even flow reversal mode) and to the external conditions.
However, individual adjustment of each vane, particularly in a stator upstream of a fan, involves multiplying the number of actuators, which reduces the reliability of the system.
The object of the disclosure is to propose a solution for orienting the vanes of a turbine engine stator, in order to straighten the flow passing through the vanes by individually adapting the pitch of the vanes, at least for a certain number of flight conditions and variations of the desired effect as a function of the azimuth of the vanes about the stator axis. Furthermore, the object of the disclosure is to achieve this aim by limiting the complexity of the means that are used.
The proposed solution is particularly, but not exclusively, applicable to the example that is described. For example, it can relate to the adaptation of the pitch of the OGVs as a function of downstream obstructions, to preserve the operability of the turbine engine, or even to the adaptation of the pitch of the vanes of a straightener at the inlet of a compressor. In particular, it can allow the pumping margin of the compressor or fan, placed upstream or downstream of the stator vanes thus controlled, to be increased by more accurately straightening the flow.